The present invention relates to a rotor assembly, and includes a method of achieving that assembly.
Specifically, the rotor assembly is of the kind wherein the blades, platforms and disc comprise an integral i.e. solid, structure.
It is known to form a single, integral structure from a plurality of metal parts, by pressing the parts together and at the same time, introducing relative reciprocatory motion therebetween, in the plane of the interfaces. The resulting friction generates heat of a sufficient intensity so as to melt or at least soften the metal on each side of the interface with the further result that the parts become one. Inevitably, some metal is displaced to form flash around the periphery of the joined volume.
The method of manufacture described hereinbefore is called "linear friction bonding", and one of its advantages is that it enables an integral structure to be achieved which is made up of parts, each of which has been manufactured in a way which generates the most desired characteristics therein.
Rotor assemblies for gas turbine engines, have been constructed by linear diffusion bonding each rotor blade to the scalloped periphery of a disc. In examples known to the applicant however, the blade platforms which, as the skilled man appreciates, cooperate to form the inner wall of the fluid flow annulus in a gas turbine engine, are either integral parts of the blades and are positioned at some point radially outwardly from the intended joint line, or alternatively are separate pieces which, after joining of the blades has been effected, are slipped into grooves in adjacent sides of respective pairs of blades. The arrangements make for a complicated structure which is difficult to achieve, bearing in mind the manipulative manner in which joining has to be effected.